SIRO-DBMS is a Spatial Information Systems database tool-kit implemented as a set of external attachments to a relational database management systems. It implements user data types through parameterised definitions of the user view of additional data types and of their internal representation. A spatial access method built on a 1-dimensional key and compatible with B-trees is also provided. Retrieval performance data with data sets of the sizes likely to be encountered in production systems are reported.